40 REPORT — 1866. 



medicine lose its doubts and diflieulties, its disagreements and deceptions, and 

 become esteemed by all as the art that can confer the highest benefit upon man- 

 kind. 



On a Magnesium Lamp. By H. Laekin. 

 The distinguishing peculiaiitj of this lamp is that it burus magnesium in the 

 form of powder, instead of riband or wire, and does not depend on clockwork or any 

 similar extraneous motive power for its action. The stream of the metal powder is 

 mixed with a small portion of gas and tine sand in its progress through the tube ; 

 they escape together at its mouth, where they are ignited and continue bui'uing 

 ■\vitla a brilliant flame. 



On the Accumulation of (he Nitroqen of Manure in tlie Soil. 

 By J. B. Laaves, F.B.S., F.C.S., cmdJ. H. Gilbeet, Ph.D., F.E.S.,F.C.S. 



The authors had been engaged for many years in an investigation in the course 

 of which they liad gTown wheat year after year on the same land for more than 

 twenty years ; on some portions -n-ithout any manure, and on others with farm- 

 yard manure, or witli various descriptions of manure. They had published the 

 results obtained in tlie field during the first twenty years of the experiments *, and 

 thej^ had been for some time, and were still engaged in investigating the composi- 

 tion of the produce gi'O-mi under the difterent conditions, and also the compara- 

 tive composition of the soils of the different plots as affected by the various treat- 

 ment. 



The point to which they chiefly confined attention on the present occasion was 

 the accumulation, and the loss, of the nitrogen which had been supplied in the 

 manure and not recovered in the increase of crop. After discussing the difficul- 

 ties of sampling, preparing for analysis, and analyzing soils in such manner as to 

 yield results applicalile to the pui-poses of their inquiiy, and describing the 

 methods they had adopted, they called attention to some of the results obtained, 

 summaries of which were brought to view in Tables hung up in the room. Tne 

 percentage, and calculated acreage, amounts of nitrogen existing in such condi- 

 tion as to be determinable by burning with soda-lime were given for the soil of 

 the first, of the second, and of the third nine inches, of eleven diftereutly -manured 

 plots, shov^-ing the amounts, therefore, to the depth of 27 inches in all. 



The accumulation of nitrogen from the residue of manuring was found to be, 

 in some cases, very considerable ; but even with equal amounts supplied, it 

 varied, both in total amount and in distribution, according to circumstances ; the 

 depth to which the umised supply had penetrated being apparently influenced by 

 the character and amount of the associated manurial constituents. The general 

 result was, that, although a considerable amount of the nitrogen supplied in 

 manure which had not been recovered as increase of crop was shown to remain 

 in the soil, still a larger anioimt was as yet unaccoimted for. Initiative results 

 indicated that some existed as nitric acid in the soil, but it was believed that the 

 amount so existiui^- would prove to be but small. In fact, it was concluded that a 

 considerably larger propoition would remain entirely unaccounted for within the 

 soil to the depth under examination than was there traceable, and the probability 

 was, that at any rate some of this had passed oft' into the drains, and some into 

 the lower strata of the soil. Finally, it was shown, by reference to field results, 

 that there was not more than one or two bushels of increase in the wheat crop per 

 acre per annum, due to the large accumidated residue of nitroo:en in the soil, not- 

 withstanding its amount was man}- times in'eater than that which would yield an 

 increase of twenty bushels or more, if applied afresh to soil othei-wise in the same 

 condition. On the other hand, it was sho-wu that the ettect of an accumulated 

 residue of certain mineral constituents was not only very considerable in degree, 

 but veiy lasting, 



* " Eeport of Experiments on the Growth of Wheat for Twenty Years in succession on 

 the same Land," Jouru. Eoy. Ag. Soe. Eng. vol. ssv. pts. 1 & 2. 



